1. Field of the Invention
The present invention relates to a traction control apparatus used to suppress spinning (no-load driving) of the drive wheels on a motor vehicle, and relates more particularly to a traction control permit/prohibit determination apparatus for determining whether traction control should be permitted or should be prohibited under various different conditions.
2. Description of the Prior Art
Traction control devices have been used for years to maintain drive stability during initial starting and acceleration of a motor vehicle, and are generally used to improve the drive performance of the vehicle. When a drive wheel starts to spin, the traction control device suppresses wheel spinning by automatically restricting engine output, even overriding depression of the accelerator by the driver, or automatically applying traction control brake pressure to the spinning drive wheel.
Engine output control-type traction control devices that function by restricting the engine output are described in U.S. Pat. Nos. 4,484,280 and No. 3,776,355, and a brake control type traction control device that functions by applying traction brake pressure to the spinning wheel is described in British patent GB8719299.
In general, brake control systems introduce certain undesirable mechanical affects, including faster wearing of the brake pads, and excessive torque between the engine parts generating the drive power and the brakes, which adversely affects the entire drive system from the engine to the wheels. Because of these problems, numerous hybrid traction control devices combining both engine output control and brake control have been developed and used.
While the traction control device is distinct from the antilock brake control system (ABS), these two assemblies can share many common parts, and the brake control system can use the ABS solenoid valve to directly increase or decrease the brake pressure.
A traction control device that uses only brake control to reduce manufacturing costs has also been proposed (British patent GB8719299).
With a traction control device that uses only brake control, however, traction brake pressure may be frequently applied and may even be applied in the medium and high speed ranges where traction control is virtually never needed. As a result, brake pad wear is accelerated, and the brake system and drive system may be adversely affected.